The small Lake of Malga Tassullo gathers the waters that descend into Val della Roccia. Located at a short distance from the malga, it is in a fascinating place, in the soft and warm landscape of the Pian della Nana, in the northeastern part of the protected area.
There are few lakes on the Pian della Nana. The plateau lacks a superficial hydrographic network, since all the rain and fusion water is rapidly drained in depth by the dense network of karstic ducts that pervade the limestone rocks. Karst has shaped depressions, dolines and swallow holes. Some basins can be temporarily occupied by ephemeral pools used for grazing livestock. Not far away, but outside the border of the Park, there are two other beautiful lakes, Salare and Durigal.